In recent years, because of miniaturization and design consideration, there is a need for more effective mounting methods for circuit board devices that are used in electronic devices such as mobile telephone terminals. In order to meet this need, there is a method for overlapping two printed boards to improve the mounting efficiency. In this case, GNDs of the two printed boards must be connected to each other so that the GNDs of the two printed boards have the same electric potential. As illustrated in FIG. 5, in case the GNDs of first printed board 210 and second printed board 220 are connected to each other, there is typically used a method of connecting the GNDs directly by means of GND connecting spring terminal 211 or the like.
Further, there is a need to prevent noise interference between the printed boards, the noise interference being caused by the proximity between the two printed boards, and there is a need to avoid effects of heat transfer such as heat conduction. Thus, as illustrated in FIG. 6, the following measures are taken in which noise generating component 311 is covered with metal shield 312 or in which a heat sink in a heat generating component is arranged so as to release the heat (regarding the heat release, refer to, for example, on page 2 or in FIG. 6 of Japanese Patent Application Laid-Open No. H11-307968).